Understanding Point-Biserial and Its Role in Medical School Assessments

When it comes to medical school assessments, measuring the quality of exam questions is essential. One tool often used for this is the point-biserial correlation coefficient. While this term might sound complex, it’s really just a way to measure how well a question distinguishes between students who generally perform well on an exam and those who don’t. Here’s a breakdown of how it works and why it matters in medical education.

What is Point-Biserial?

In simple terms, the point-biserial is a statistical measure that tells us whether a question on a test is effective at distinguishing high-performing students from low-performing ones. In other words, it helps us see if the question is doing its job. Each question on a test should ideally be more likely answered correctly by students who understand the material well and less likely by those who don’t.

How Does It Work?

When students take a test, each question can receive a point-biserial score. This score tells us how strongly the students' performance on that question is related to their overall performance on the test.

• A high point-biserial score (usually above 0.2) means that students who did well on the exam also got this question right more often than students who didn't do as well. This indicates that the question is effective in measuring students’ understanding of the material.

• A low or negative point-biserial score (0 or below) suggests that the question may not be useful. If students who did poorly on the test answered it correctly as often as high-performing students, it might mean the question was either too easy, confusing, or even misleading.

Example of Point-Biserial in Action

Let’s imagine an anatomy exam question: “What is the longest bone in the human body? ”

• High point-biserial score: Most of the high-performing students (those who scored well on the entire exam) answer this question correctly by choosing "femur," while low-performing students often choose incorrect answers.

• Low or negative point-biserial score: Both high- and low-performing students answer this question correctly, or maybe high-performers get it wrong just as often as others. This could mean the question doesn’t really help in differentiating between levels of understanding.

By analyzing the point-biserial scores of questions, instructors can identify which questions are contributing to the assessment’s overall effectiveness and which ones may need improvement.

Why Point-Biserial Matters in Medical School Assessments

Point-biserial correlation helps medical schools design exams that accurately reflect students' grasp of the material. It ensures that assessments aren't just testing memorization but are instead useful indicators of critical understanding and clinical reasoning. This ultimately leads to better-prepared students, ready to tackle clinical rotations, licensing exams like the USMLEs, and their future medical careers.

How to Implement Point-Biserial in Your Medical School

If your institution wants to improve the quality of its assessments and gain deeper insights into student performance, point-biserial analysis can be a powerful tool. At Atomic Medical Education (AME), we specialize in curriculum development and can guide you through the process of integrating point-biserial and other assessment techniques into your program.

Interested in learning more? Contact us at AME to explore how point-biserial analysis can enhance the accuracy and fairness of your assessments, ensuring they meet the needs of today’s medical students and tomorrow’s healthcare professionals.